1. Field of the Invention
The present invention relates to semiconductor fabrication techniques, and in particular, to a method for fabricating a semiconductor device with a fuse element.
2. Description of the Related Art
For redistributing memory circuits and logic circuits in semiconductor devices, fuse elements are commonly applied. For example, defective memory cells or circuits in memory devices such as dynamic random access memory (DRAM) devices and static random access memory (SRAM) can be redistributed with a new active circuit by blowing up a fuse element in related circuits. Such circuit redistribution design incorporating fuse elements is helpful for improving product yield and reducing abandoned wafers with process deficiencies.
Fuse elements are typically integrated as a part of one of the metallization layers of semiconductor devices. One or more interlayer dielectric layer and a topmost passivation layer are provided over the fuse elements. Therefore, prior to blowing up of the fuse element by methods such as a laser trimming process, the passivation layer and the interlayer dielectric layers formed over the fuse elements are needed to be removed to form a laser access window and expose the fuse elements covered by an interlayer dielectric layer with a predetermined thickness. The interlayer dielectric layer covering the fuse elements exposed by the laser access window protects the fuse elements from be subjected to corrosion or breakdown. The thickness of the interlayer dielectric layer left in the laser access window is proportional to the energy of the laser used in the laser trimming process.
The laser access window is typically formed after formation of the topmost passivation layer and the metallization layer and is simultaneously formed during patterning of the topmost passivation layer for forming an opening to expose a bond pad therein by methods such as an etching process.
The etching process for forming the laser access window not only passes through the topmost passivation layer but also passes through one or more interlayer dielectric layers under the passivation layer. Controlling the film thickness and uniformity of the interlayer dielectric layer left over the fuse elements in the laser access window is difficult.
If the interlayer dielectric layer left over the fuse elements in the laser access window is too thick, the fuse elements may not be blown up in a sequential laser trimming process. In addition, if the interlayer dielectric layer left over the fuse elements in the laser access window is too thin, the fuse elements may be corroded by moisture and air in the environment or ruined during the etching process for forming the laser access window prior to the laser trimming process. The undesired issues may affect reliability of a semiconductor device having the fuse elements.